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The generate_series Table-Valued Function

1. Overview

The generate_series(START,STOP,STEP) table-valued function is a loadable extension included in the SQLite source tree, and compiled into the command-line shell. The generate_series() table has one visible result column named "value" holding integer values and a number of rows determined by the parameters START, STOP, and STEP. The first row of the table has a value of START. Subsequent rows increment by STEP to a value not exceeding STOP.

The generate_series() table has additional, hidden columns named "start", "stop", and "step" whose values are the effective values of START, STOP and STEP as provided or defaulted. It also has a rowid, accessible by its usual names.

Omitted parameters take on default values. STEP defaults to 1. STOP defaults to 4294967295. The START parameter is required as of version 3.37.0 (2021-11-27) and later and an error will be raised if START is omitted or has a self-referential or otherwise uncomputable value. Older versions used a default of 0 for START. The legacy behavior can be obtained from recent code by compiling with -DZERO_ARGUMENT_GENERATE_SERIES.

1.1. Equivalent Recursive Common Table Expression

The generate_series table can be simulated for positive step values using a recursive common table expression. If the three parameters are $start, $end, and $step, then the equivalent common table expression is:

WITH RECURSIVE generate_series(value) AS (
  SELECT $start
  SELECT value+$step FROM generate_series
   WHERE value+$step<=$end
) ...

The common table expression works without having to load an extension. On the other hand, the extension is easier to program and faster.

2. Usage Examples

Generate all multiples of 5 less than or equal to 100:

SELECT value FROM generate_series(5,100,5);

Generate the 20 random integer values:

SELECT random() FROM generate_series(1,20);

Find the name of every customer whose account number is an even multiple of 100 between 10000 and 20000.

SELECT customer.name
  FROM customer, generate_series(10000,20000,100)
 WHERE customer.id=value;
/* or */
SELECT name FROM customer
 WHERE id IN (SELECT value
                FROM generate_series(10000,20000,200));

This page last modified on 2023-05-01 21:49:55 UTC

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